Embodiments relate to communications networks and to RF amplifiers. Embodiments relate to variable gain amplifiers.
Amplifiers with wide gain programmability range that is linear in dB scale may be an integral part of many systems. Building an amplifier with large variable gain range which can be controlled linearly in dB scale may be difficult in CMOS processes.
These amplifiers may consume large amounts of power to maintain linearity at high output power mode. This power may be wasted toward ground while operating in low power. In certain systems (for example, a wireless communication transmitter) such amplifiers may be operated with low power and may therefore waste a lot of energy.
In several different types of communications systems a final RF power amplifier may be expected to deliver large output power while maintaining good linearity. This may often result in large power consumption. Such amplifiers may have been operated with low output power most of the time and thus large amounts of power may be wasted.
Variable gain amplifiers (VGA) may be useful in many wireless communications technologies and a final RF power transmission may be expected to have a wide gain programmability range that is linear in the dB scale. Building a VGA that is linear in the dB scale in a CMOS process may be difficult.
In some design implementations, almost all of the functional blocks of a power amplifier may have large dynamic ranges to maintain linearity in dB gain steps. Such a design may waste a lot of power at low gain mode. The linearity of a VGA at high output power determines the bias current in the amplifier and hence at low output power mode, most of this is wasted towards ground. Attempts to address this issue may increase complexity and add circuitry, and can introduce additional problems to overcome.
There remains a need, therefore, for a VGA architecture with built-in power optimization that can work with large linear-in-dB gain programmability range and also include a fine and accurate gain step.